The basic purpose of the project is to study the physiology of dental plaque bacteria with a view to identifying physiological peculiarities that could be exploited for control of cariogenic activities. The project involves growth of oral bacteria in dense cultures in which conditions are crowded as they are in dental plaque. However, for physiological studies, it is necessary that such cultures yield relatively uniform populations. Thus, for example, agar-plate colonies will not do because they have highly heterogenous populations with many dead cells. Our most promising culture system is pellet culture in which the bacteria are grown in centrifuged pellets. The cells can be "fed" simply by resuspending them in fresh or used medium and then repelleting them. Many oral bacteria will grow in these conditions to yield relatively homogeneous populations that can be used for physiologic studies. BIBLIOGRAPHIC REFERENCES: Marquis, R. E. and T. R. Corner. 1975. Isolation and properties of bacterial protoplasts. Fourth International Symposium on Yeast and Other Protoplasts, Academic Press, London. Marquis, R. E., K. Mayzel and E. L. Carstensen. 1976. Cation exchange in bacterial cell walls. Can. J. Microbiol. in press.